Example:

By printing out the file name in a format that Jenkins will understand

The above mechanism has a problem that your test needs to know about where your test driver is producing reports to. This 2nd approach eliminates that problem by simply letting you print out arbitrary file names to stdout/stderr in the following format:

[[ATTACHMENT|/absolute/path/to/some/file]]

Each "ATTACHMENT" should be on its own line, without any text before or after. See Kohsuke's post for more details.